Allonemobius Shalontaki, a New Cryptic Species of Ground Cricket (Orthoptera: Gryllidae: Nemobiinae) from the Southwestern United States
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SYSTEMATICS Allonemobius shalontaki, a New Cryptic Species of Ground Cricket (Orthoptera: Gryllidae: Nemobiinae) from the Southwestern United States 1 W. EVAN BRASWELL, LEANNA M. BIRGE, AND DANIEL J. HOWARD Department of Biology, New Mexico State University, Las Cruces, NM 88003 Ann. Entomol. Soc. Am. 99(3): 449Ð456 (2006) ABSTRACT A new species of ground cricket in the genus Allonemobius (Hebard) is described from the southwestern United States. Like many singing Orthoptera, this species is morphologically cryptic and most easily distinguished from related species by using molecular characters and male calling song traits. We describe Allonemobius shalontaki as a new species and present data suggesting its repro- ductive isolation from congeneric species. Allonemobius shalontaki exhibits a unique male calling song and possesses a distinct allozyme genotype. Additionally, we present an electrophoretic key to the genus and propose phylogenetic relationships among species. KEY WORDS Allonemobius, calling song, Nemobiinae, Orthoptera, phylogeny Among the singing Orthoptera many closely related, ferentiation (Chu and Howard 1998, Mousseau and reproductively isolated species are divergent in eco- Howard 1998, Roff and Mousseau 1999, Roff et al. logical and sexual traits yet exhibit little or no mor- 1999), life history evolution (Tanaka and Brookes phological divergence. Species with these character- 1983, Bradford and Roff 1995, Carrie´re et al. 1997, Roff istics are known as cryptic species and pose particular and Bradford 2000, Olvido et al. 2003), hybrid zone problems for taxonomy (Alexander 1962, Walker dynamics (Howard 1986, Howard and Waring 1991, 1964). Frequently among these groups, new species Howard et al. 1993, Chu et al. 1995), competition and are recognized not by museum specimens but rather habitat selection (Howard and Harrison 1984a, by detailed ecological and behavioral observations. 1984b), and reproductive protein evolution (W.E.B., For example, crickets of the genus Allonemobius unpublished data). Their role as important study sys- (Hebard) were initially constrained to a single species tems may be because of their abundance. Indeed, (DeGeer 1773; Alexander and Thomas 1959, Vickery these species have been studied most intensively along and Johnstone 1970). Intense study by Fulton (1931, the eastern coast of North America where they are 1933, 1937) revealed physiological distinctions be- perhaps the most abundant singing orthopteran. How- tween populations that lead to the eventual descrip- ever, most species in this genus are rarely encountered tion of several unique species (Alexander and Thomas and relatively unknown. The majority of work on this 1959). Despite these intense ecological, behavioral, genus has focused on the three species exhibiting the and morphological studies, additional cryptic species highest abundance on the east coast: Allonemobius were found after detailed genetic work (Howard 1983, Howard and Furth 1986). fasciatus (De Geer), Allonemobius socius (Scudder), All members of the genus Allonemobius are small, and Allonemobius allardi (Alexander & Thomas). Un- ground-dwelling omnivores with most species dis- fortunately, other members of this genus remain in tributed broadly across eastern North America. They their shadow. have become well known through their role in the Although little work has been done outside of east- description of major patterns and processes in ecology ern North America, the presence of geographic bar- and evolution. Species in this genus have been used to riers and diverse habitats in western North America, elucidate the process of speciation (Gregory and suggests that there may be many undiscovered Howard 1993, 1994; Gregory et al. 1998; Doherty and isolated populations in the west. We know of only Howard 1996; Veech et al. 1996; Howard et al. 1998), two taxonomic studies of Allonemobius in the west; sexual selection (Howard and Gregory 1993; Gregory Vickery and Johnstone (1970) collected extensively and Howard 1996; Fedorka and Mousseau 2002a,b), across Canada, and Weibel (1996; see also Weibel and sexual conßict (Fedorka and Mousseau 2004), mating Howard 2000a,b) sampled Allonemobius across the system evolution (Sadowski et al. 2002), genetic dif- western United States. Weibel (1996) discovered sev- eral new populations that she suggested were com- 1 Corresponding author, e-mail: [email protected]. posed of new species. Her work suggests that at least 0013-8746/06/0449Ð0456$04.00/0 ᭧ 2006 Entomological Society of America 450 ANNALS OF THE ENTOMOLOGICAL SOCIETY OF AMERICA Vol. 99, no. 3 some species of Allonemobius remain to be discovered. Table 1. Allele frequency of new populations with number of Herein, we describe one such species. individuals in parentheses Locus Allele Salado, TX Atoka, OK Materials and Methods MDH 1.6 0.9 (9) 1.0 (22) 1.0 0.1 (9) In August1999, W.E.B. collected crickets at the Con- HK 1.0 1.0 (8) 1.0 (15) federate Memorial Museum and rest stop along U.S. IDH 1.5 0.9 (9) 1.0 (21) Hwy. 69 in Atoka, OK, and south of Salado, TX, at mile 1.0 0.1 (9) marker 283 on Interstate Hwy. 35. The Atoka collec- ME 1.0 1.0 (9) 1.0 (22) AAT (GOT) 2.0 0 0.14 (18) tion was transported back to the laboratory alive and 1.0 0.69 (7) 0.86 (18) used for calling song, genetic, and morphological 0.8 0.31 (7) 0 analyses. The Salado collection was immediately fro- PGI 1.6 0 0.02 (22) zen in liquid nitrogen, transported back to the labo- 1.17 0.5 (1) 0.93 (22) Ϫ Њ 1.0 0.5 (1) 0.05 (22) ratory, and transferred to 80 C until used for genetic EST-1 1.1 0.13 (8) analyses. 1.0 0.5 (8) Genetic analysis of individual crickets was performed 0.9 0.31 (8) using allozyme electrophoresis. Electrophoretic analysis 0.8 0.06 (8) G-PGD 1.0 1.0 (8) 1.0 (22) was based on 14 enzyme loci, including isocitrate de- PGM 1.0 1.0 (9) 1.0 (22) hydrogenase (IDH), malate dehydrogenase (MDH), MPI 1.0 1.0 (9) hexokinase (HK), aspartate aminotransferase (AAT), G6PD 1.0 1.0 (1) esterase-1 (EST-1), phosphoglucose isomerase (PGI), ACP 1.0 1.0 (5) ␣-GPD 1.0 1.0 (5) 6-phosphogluconate dehydrogenase (6-PGD), malic en- GP 1.0 1.0 (5) zyme (ME), phosphogucomutase (PGM), mannose-6- phosphate isomerase (MPI), acid phosphatase (ACP), Allele names are based on the starch electrophoretic mobility of the ␣-glycerophosphate dehydrogenase (␣-GPD), glucose- allele relative to that of the most common allele in A. fasciatus. 6-phosphate dehydrogenase (G6PD), and general pro- tein (GP). A single hind leg was removed from each cricket and analyzed as in Howard (1982). these analyses included both the electrophoretic data Morphological analyses were performed on crickets mentioned above as well as data previously published from Atoka that had been previously identiÞed by by Howard (1983). Pairwise genetic distances were electrophoretic and calling song analysis. Eight mor- estimated using the methods of Nei (1972), Cavalli- phological traits were measured, including shared and Sforza and Edwards (1967), and Reynolds et al. sex-speciÞc characters. These characters were chosen (1983). Pairwise distances were used to reconstruct to match those used by Howard and Furth (1986) in phylogenetic relationships by using both least squares describing other members of the genus. For both and minimum evolution methods with and without the sexes, we measured the body length (Lb), pronotum assumption of a molecular clock in the FITCH and length (Lp), pronotum width (Wp), and hind femur KITCH programs. Neighbor-joining and unweighted length (Lf). For males, we measured characters of the pair-group methods with arithmetic average methods tegmen as these characters may affect calling song. were used with the NEIGHBOR program. Data sets Tegmen characters were measured as in Fulton (1931) were resampled 1000 times to generate bootstrap sup- and Howard and Furth (1986) and included the stridu- port using SEQBOOT, and consensus trees were ob- latory vein measured from the mesal origin to the tained using CONSENSE. ulnar vein (Tg1), the distance from the ulnar vein to the lateral border of dorsal tegmen surface (Tg2), and Results the distance from the stridulatory vein to the apex of the tegmen (Tg3). For females, we measured the We genetically analyzed a total of 31 crickets from length of the ovipositor (Lo). the two collections (22 from Atoka, OK, and nine from To record male calling songs, males were individ- Salado, TX) for 14 electrophoretic loci. Most loci are ually isolated in 17- by 12- by 6-cm plastic boxes with invariant and have alleles typical of the A. fasciatus mesh covers. Songs were recorded using a Realistic species group (Table 1). However, two allozyme loci Cardioid dynamic microphone and a Sony MZ-R50 are Þxed for novel alleles in one population. These recorder at 22Ð24ЊC. Songs were analyzed using the novel alleles occur at high frequencies in the other Canary software (Cornell Laboratory of Ornithology, population. A third locus exhibits variation in both Ithaca, NY; Charif et al. 1995). By isolating individual populations, with high frequency alleles that are rare males, we ensured that songs produced were not in within the A. fasciatus group. In the Atoka population, response to stimulus from females or other males; as a the allele for the MDH enzyme is Þxed and migrates result, the songs recorded are calling songs and not at 1.6 times the distance as the most common allele courtship or aggressive songs. in A. fasciatus. Similarly, the IDH locus is Þxed for a Phylogenetic analyses were performed to assess the novel allele in the Atoka population, which migrates relationship of newly collected crickets to the remain- 1.5 times the distance as the most common allele in ing members the genus Allonemobius by using pro- A.